The following description relates to the technical field of semiconductor components, specifically it refers to a method of structuring a layer in a semiconductor component.
In the following context the term “semiconductor component” relates in general to integrated circuits, chips, as well as single semiconductor components like for example analog or digital circuits or single semiconductor components like semiconductor memory elements, for example, functional storage components (PLAs, PALs etc.) and array storage elements (ROMs or RAMs, especially SRAMs and DRAMs).
Beside other applications, for example, micromechanical components, the method of structuring can be used to manufacture stabilizing support structures of capacitors of DRAM-components. According to the cell concept one may distinguish between trench capacitors and stack capacitors. Trench capacitors are formed in the substrate and therefore are arranged underneath the selection transistors of the respective cell. On the other hand, stack capacitors are arranged above the substrate and above the selection transistors.
In terms of shape, both capacitor types may have a cylindrical form. The cross section may be round or elliptical and does not need to be of the same shape over the axial course of the capacitor. For sake of simplicity, the shape is referred to as tube, whereas different areas and sizes of cross sections at different axial positions are possible. Furthermore the tubes may include an overhang, i.e. they may have a larger cross section in a top portion compared to a lower portion.
To increase the capacitance of a capacitor C
  C  =            ɛ      o        ⁢          ɛ      r        ⁢          A      d      with the surface A, the distance between the electrodes d and the dielectric constant ∈r, various measures are applied. One measure may be the increase of the aspect ratio of the capacitor tube and thereby the increase of the capacitor surface A.
The structure of the stack capacitors above the substrate leads to the problem of mechanical stability of the capacitor arrangement. For example, a process using liquids (e.g., a wet etch or a wet rinse) may lead to a collapse of the tubes due to capillary forces.
Various techniques are applied for the mechanical stabilization of the stack capacitor.
In general, support structures are introduced which are arranged in an upper portion of the capacitor tube and which connect adjacent tubes with each other. This may prevent a bending of the capacitor tubes. However, it must be ensured that the material underneath the support structure can be at least partly removed. To achieve this, a structuring of the support material needs to be done in order to create openings.
One possibility to structure the support material is the use of the so called mask process. In a first step, a photoresist is deposited. The resist is exposed through a mask and the exposed or unexposed parts of the resist are removed. The structure of the resist layer is transferred in a subsequent step into the support material. Disadvantage of such a method is the need of a mask for this process and additional steps like the deposition of the photoresist, the exposure and the structuring of the resist, etc. are required. This impacts the cost of such a manufacturing process of a semiconductor component.
Kim et al., “A Mechanically Enhanced Storage Node for Virtually unlimited Height (MESH) Capacitor Aiming at sub 70 nm DRAMs”, IEDM Tech. Dig., p. 69-72 (2004) illustrates a support structure of a stack capacitor made from silicon nitride. The structuring of the support structure is performed by using the so called spacer technology. A conformal silicon nitride layer is deposited onto the capacitor tube. The support material is subsequently structured by using dry etch step. Using this method, the structuring is self aligned and no mask step is required.
A similar process is proposed by Manning in U.S. Pat. No. 7,067,385. A spacer is used for the structuring of the support material as well.